<!--
 * @Description: 
 * @Author: xiongkuobiao
 * @Date: 2023-02-20 16:40:40
 * @LastEditors: xiongkuobiao
 * @LastEditTime: 2023-02-20 16:44:57
-->
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body></body>
  <script>
    // let xhr = new XMLHttpRequest();
    // readyStatus == 4  state == 200
    // open
    // send之前设置请求头和响应头

    // 用promise封装

    // return new Promise(function (resolve, reject) {
    // if(成功) resolve(res)
    // if(失败) reject(err)
    // });
  </script>
</html>
